Mechanical and electrical equipment, which is to be used in a difficult environment must often be protected thereagainst in order not to be damaged or interrupted in the its function.
In many cases enclosures are used which are type plastics. For more demanding applications laminates are used, for instance composed by several plastic materials, or by plastics and other materials such as metal sheets, in the established art. Laminates of plastics and metal have the advantage of being both non-permeable to diffusion of water vapour and of being electrically shielding. Depending on the metal layer and in particular the thickness thereof both flexible and stiff laminates can be obtained. The latter ones can also for certain material compositions be deep drawn, that provides a simple manufacturing method of boxes and lids for sealing and encapsulation.
The manufacture of plastic/metal laminates are usually performed in one of the two following manners:
1. One of the surfaces, which are to be joined, is coated with a polyurethane glue having a sticky consistency, whereafter the surfaces are pressed together in heat. The glue contains solvent, which must be removed by drying the glued materials in large, space-consuming drying machines. Moreover, an afterhardening of the glue must be made by storing the laminate for a couple of months in order for the water to diffuse into the glue for hardening it. The glue joints have a bad humidity resistance. PA0 2. The plastics layer is extruded in the shape of a thin layer on a metal sheet path. High requirements are put on the wide slit nozzle used. Furthermore, commercially used extruders and their screws are large, which results in that a readjustment for extrusion of different materials is difficult, circumstantial and very time-consuming to perform. This is unsuitable for manufacturing laminated materials to be used in small series, when a flexible manufacturing method is required, such as is the case in making different types of capsules for example for delicate electronic circuits.
Also, plastic/metal laminates can be manufactured where the bonding to the metal layer is provided by a layer of ionomer plastics, where the bonding layer also can be the entire plastic component of the laminate, see e.g. the European patent application EP-A2 0 057 994, U.S. Pat. Nos. 5,376,446, 4,439,810, 3,725,169 and the German published patent application DE 2 233 958.